Master cylinder problem!

[DBossMan]

I need to replace the m/c on my 72 F250 Crew (with power front dual piston disk, rear drum).

I have removed the old one and been to several autoparts stores. Unfortunately, the part they pull is not the same size as the one that came off the truck. The one that came off the truck is much much larger. The resevoirs are larger, the cap is much larger, etc.

The bolt holes line up, but I'm concerned about giving up the size/capacity of the larger m/c.

Any ideas? Rebuilding is probably not an option b/c I dont know what I have. In fact, I've never been able to find a cover gasket big enough.

Tim

[68F250]

Ask them to pull one for a F350 w/ power discs.

[DBossMan]

Good thought.

However, according to PartsAmerica.com, both the 250 and 350 use the same m/c for power front disc setups.

I'm starting to compare part numbers across years (ie 72 vs 73-79, etc).

[68F250]

When comparing with the later trucks, only look at ones listed for the dual piston calipers. The single piston calipers use a mc with the lines coming out the other side.

[DuckRyder]

According to the NPD catalog,

1968-1972 F250 4x2 with power disc (exc 71?) use a 2140-18

That same number is also used by 68-72 F350 and 76 F250 4x4 and 73-74 F250 $x2 with heavy duty brakes and 6200-8100 GVWR

it is a 1-1/4 diameter.

FWIW

[68F250]

I've observed two different mc's for the F250/F350. One looks like what you'd expect to see and the other one is a lot taller. Like to get to the bottom of this. 1" diameter is for drum brakes and 1 1/4" is for discs.

[willowbilly3]

I'm not sure if the parts guy just screwed up and was coverng his butt or what but I had to get one for a 73 to fit my 72 due to a difference in bore size. My 72 has an August 72 production date. F-250, 6200 gvw, dual piston discs. It doesn't look bigger than any other one but I always suspected the operatio of it. Although I couldn't complain about the operation, I never got more than 15,000 miles or so out of pads and the rear shoes still looked fine at 0ver 100,000. It locks all 4 at the same time on ice or gravel.

[DBossMan]

DuckRyder, your comment about NPD prompted me to go look at their catalog. It was one of the few I hadn't already looked at.

The footnotes on Page 41 of their catalog point out that the two m/c's pictured on the page are essentially the same, EXCEPT one is 2 5/8 " wide at the cap, and the other is 3 1/8" wide.

Went out and measured mine. Low and behold, its the 3 1/8 wide version.

Next step will be to give call them a call.

Thanks.

Tim

[DuckRyder]

Glad it helped Tim.

FWIW, I do not think those footnotes are directly related to your application, but would caution you to question them thoroughly about them, as I believe they may have at least part of their description backwards.

I can assure you one thing, the picture on page 41 of the third edition of an F-2140-8 is not a 2140-8 and it looks like the picture of the 2140-7. I have a 2140-7 on order and was going to post once I get it and can confirm. I HOPE that it looks like the picture they have of a 2140-8 because that’s the one I need.

If your master cylinder is the original, the determining factor seems to be if the reservoirs are equal sized or not.

They are nice parts though and the ones I have gotten have been Wagner.

[DBossMan]

DuckRyder: Agreed. The footnotes just confirmed for me that there were different sized resevoirs. Until I read that, I wasn't sure what to think.

What's not clear to me is:

1. Which size is correct for my truck? Wide or tall.
2. Does the resevoir size have any impact on performance?

I will call NPD on Monday and see what they can tell me.

[DuckRyder]

From my experience, the port sizes are the big difference.

All things being equal (piston size particularly) I wouldn't think that the reservoir would impact performance in most cases. I guess that perhaps it is possible under severe use that a larger reservoir would be more fade resistant.